@PHDTHESIS{ 2017:798912526,
 	title = {Hybrid synchrony virtual networks},
 	year = {2017},
 	url = "http://tede2.pucrs.br/tede2/handle/tede/7344",
 	abstract = "In the last three decades of research in Distributed Systems (DSs), one core aspect discussed
 is the one of synchrony. \Vith an asynchronous system, we make no assumptions
 about process execution speeds andj or message delivery delays; with a synchronous
 system, we do make assumptions about these parameters [Sch93b]. Synchrony in DSs impacts
 directly the complexity and functionality of fault-tolerant algorithms. Although a synchronous
 infrastructure contributes towards the development of simpler and reliable systems,
 yet such an infrastructure is too expensive and sometimes even not feasible to implemento
 On the other hand, a fully asynchronous infrastructure is more realistic, but some problems
 were shown to be unsolvable in such an environment through the impossibility result by
 Fischer, Lynch and Paterson [FLP85]. The limitations in both fully synchronous or fully
 asynchronous environments have led to the development of partial synchronous distributed
 systems [CF99, Ver06].
 In a study of partial synchronous distributed systems functionality, and of Virtual Networks
 (VNs) properties, we found that there are several challenges for this kind of systems
 that can be solved with VNs due to the properties that virtualization brings. For example a)
 resources sharing provided by VNs allows decreasing the cost when sharing the synchronous
 portion of the physical infrastructure, b) isolation provided by the VNs nature can benefit
 the coexistent DSs on same physical infrastructure that demand certain leveI of isolation, c)
 resilience guaranteed through the Virtual Networks Embedding (VNE) process that allows
 allocating spare resources beside the primary ones for virtual networks that require availability
 guarantees, for example fault tolerant DSs. In our work, we argue that VNs and
 a suitable VN embedding process offer suitable environment for running distributed applications
 with partial synchrony. This has led to the abstraction of new type of VNs: The
 Hybrid Synchrony Virtual Networks (HSVNs).
 In this thesis, we introduce the general idea of Hybrid Synchrony Virtual Networks
 (HSVNs) motivated by the hybrid synchronous DSs, and we branch our work into two
 branches: a) Space-HSVNs addressed to spatial hybrid synchronous DSs, and b) TimeHSVNs
 addressed to the time hybrid synchronous DSs. In spatial hybrid synchronous DSs, the hybrid synchronous physical infrastructure is composed of subsets of synchronous and
 asynchronous components, and each of these subsets maintains its synchrony status through
 time (i.e., synchronous subsets remain synchronous and asynchronous ones remain asynchronous).
 In time hybrid synchronous DSs, the hybrid synchronous physical infrastructure
 is composed of subsets of nodes and links that can alternate their synchrony status through
 time (i.e., the components behave synchronously during time intervals, and asynchronously
 during other time intervals).
 The main contributions of this thesis are: a) characterize the HSVNs in its two types
 Space-HSVNs and Time-HSVNs to reflect both the synchrony space-variant and time-variant
 nature ofDSs; b) propose a suitable embedding framework for both Space-HSVNs and TimeHSVNs,
 and c) provide an evaluation of the embedding mo deIs addressed to the HSVNs.",
 	publisher = {Pontifícia Universidade Católica do Rio Grande do Sul},
 	scholl = {Programa de Pós-Graduação em Ciência da Computação},
 	note = {Faculdade de Informática}
}